Isoflavone, which is contained in a soy food in large amount, is known as a functional component having effects of relieving a climacteric disorder such as malaise, preventing osteoporosis, preventing hyperlipidemia and arteriosclerosis, and preventing breast cancer and prostate cancer. Recent studies clarified that daidzein, which is one of the isoflavone, is metabolized by internal enteric bacteria to equol having stronger estrogenic action and antioxidation effect (see FIG. 1). Accordingly, equol has been noted as a main active ingredient performing the above effects in the body.
It has been reported that production of equol from daidzein in the body does not equally occur among all human, the equol-producing ability varies among individuals, and 30 to 50% of human being has equol-producing ability. Thus, research for enteric bacteria having equol-producing ability (an equol-producing bacteria) has intensely been carried out, and Bacteroides ovatus, Streptococcus intermedius, Streptococcus constellatus, Lactococcus garvieae, Slackia spp. TM-30 strain, Bifidobacterium adolescentis TM-1 strain, Bifidobacterium breve JCM 1273, Proprionobacterium freudenreichii, Bifidobacterium lactis, Lactobacillus acidophilus, Lactococcus lactis, Enterococcus faecium, Lactobacillus casei, Lactobacillus salivarius, SNU-Julong732, gram positive bacterium do03, and Slackia sp. YIT 11861 (FERM BP-11231) have been reported as equol-producing bacteria (Patent Literature 1).
As described above, equol has various activities, and is expected to have preventive effects on sex hormone dependent diseases such as breast and prostate cancers. Thus, determining whether an individual has equol-producing ability or not is important.
Methods for determining whether a test subject has equol-producing ability or not include a method of detecting and measuring blood or urine equol metabolized from daidzein by an equol-producing bacteria in the present situation. A drawback to the method is that an amount of daidzein in blood or urine, and further an amount of equol vary depending on an amount of soybean intake before blood or urine collection. Specifically, when a test subject does not ingest soybean, equol is not detected in blood or urine. Thus, there is a risk that such a test subject can be misjudged to have no equol-producing ability whereas the test subject has an equol-producing bacteria.
On the other hand, a method for determining whether a test subject has equol-producing ability or not by presence or absence of an equol-producing bacteria may be possible. However, a method for precisely detecting the presence of all equol-producing bacteria has not been established, and such a method has not been reported.